There are many applications in which a plurality of threaded connectors, usually arranged spaced from each other along a circle, have to be tightened or loosened. Until now such threaded connectors have been individually tightened, which of course is quite a time-consuming task. Hydraulic wrenches are rather heavy and may weigh up to 200 pounds, and such heavy wrenches have to be lifted and lowered by a crane to apply such wrenches to successive threaded connectors to be tightened or loosened. The set-up time for moving the wrench from one to the next threaded connector may therefore be from 5 minutes up to half an hour. While for some special applications apparatus have already been provided by means of which several bolts or threaded connectors could be tightened or loosened simultaneously, such known apparatus is extremely complicated, heavy and expensive, so that the handling thereof is likewise difficult.
In many applications, the available overhead space for applying a hydraulic wrench is so small that hydraulic wrenches of known constructions could not be used, and in such cases box wrenches have been used to which hammer blows have been applied to tighten or loosen a threaded connector. Of course in such cases a proper tightening of the threaded connector with a predetermined force could never be obtained.
Especially in loosening a threaded connector, which may be partly corroded, a greater force may be required than for originally tightening the same to a predetermined degree. In such case, a hydraulic wrench with a power for originally tightening the threaded connectors to the desired degree may be insufficient for loosening the same again.